Unfortunately, insecticides are not toxic only for the target insects, but also for a large array of the fauna, and for humans as well. And the effects in humans go from various symptoms to severe cancers, such as breast cancer. Usually, breast cancers are associated with impairments in the balance of sex hormones. The main chemical resulted from the metabolic breakdown of DDT, one of the most common insecticides, had been connected to aggressive breast cancer tumors, but a new research published in the journal "Breast Cancer Research" also explains that it impacts the hormone-sensitive breast cancer cells.

The team at the Universite Laval and Institut national de sante publique in Quebec, Canada, has found that this metabolite, called 1,1- dichloro - 2,2 - bis(p-chlorophenyl)ethylene (p,p'-DDE), can indeed boost breast cancer development. It seems that p,p'-DDE impairs the androgen signaling pathway that stops the growth in breast cancer cells.

The team checked the action of p,p'-DDE on the multiplication of CAMA-1 cells, a human breast cancer cell type possessing the estrogen receptor alpha (ERa) and the androgen receptor (AR), no matter the amounts of both types of hormones (estrogens and androgens).

The team followed p,p'-DDE-induced changes in the cells' metabolism and the activity of sex hormone controlled genes like ESR1 and CCND1, the latter encoding a main protein acting in cell proliferation.

When estrogens and androgens were added in the cell culture medium, higher levels of p,p'-DDE boosted the division of CAMA-1 breast cancer cells, but also of MCF7-AR1 cells, an estrogen sensitive cell type engineered to overexpress the AR.
The team added the powerful androgen dihydrotestosterone together with estradiol (the major human estrogen) and the result was that less CAMA-1 cells entered in the S phase and had decreased activity of ESR1 and CCND1, compared to cells exposed to estradiol alone. These androgen-induced effects were eliminated by p,p'-DDE, with similar effect to the powerful antiandrogen hydroxyflutamide.

"Our results suggest that in addition to estrogenic compounds, which have been the main focus of researchers over the past decades, chemicals that block the AR could favor breast cancer progression," said lead researcher Pierre Ayotte.

Now, the team is investigating other environmental toxins, encountered in the blood of women, which have estrogenic or antiandrogenic effects.